1. Field of the Invention
The present invention relates to an infrared light irradiating lamp for a vehicle which can irradiate a light of a light source bulb having a filament as an infrared light by using a reflector, an infrared light transmitting filter and a projection lens.
2. Background Art
There is an infrared light irradiating lamp for a vehicle which is loaded onto a car and illuminates a forward part of a vehicle with an infrared light, and can process a photographed image to confirm an obstacle together with a CCD camera having a near-infrared sensitivity or less (for example, see Patent Document 1).
As shown in FIG. 8, an infrared light irradiating lamp 1 for a vehicle of this type has such a structure that a light source bulb 9 to be a visible light source and a reflector 11 taking an almost elliptical spherical shape are disposed in a lighting chamber 7 formed by a lamp body 3 and a front lens 5, and an infrared light transmitting filter 13 in which an infrared light transmitting film for reflecting a visible light component and transmitting an infrared light component is formed in a whole surface region of a glass plate is provided between the light source bulb 9 and the front lens 5 in order to close a whole front opening portion of the lighting chamber 7.
In general, the light source bulb 9 is attached in a so-called rear inserting structure in which it is inserted from a rear part of the reflector 11 along an optical axis Ax of a lamp emitting light and is constituted in such a manner that a whole light emitted from a light source toward the front lens 5 passes through the infrared light transmitting film. A visible light component of the light of the light source which is reflected by the reflector 11 is cut when the light passes through the infrared light transmitting film, and the light is mainly changed into a light having only an invisible infrared light component and is emitted and distributed forward from the front lens 5.
An infrared light irradiating region in the forward part of the vehicle is photographed by means of a CCD camera having a near-infrared sensitivity or less which is provided in the front part of the car and is processed by an image processing device, and is displayed on a monitor screen in a vehicle compartment. A driver can confirm a person, a lane mark and an obstacle in a distant place over the monitor screen for displaying a field of view in the forward part of the vehicle.
However, a conventional infrared light irradiating lamp for a vehicle is provided with an additional light source for an infrared light. For this reason, the number of components is increased and a man-hour for attaching the light source for an infrared light is also increased so that a cost is increased. Therefore, there has been proposed an infrared light irradiating lamp for a vehicle which can utilize an existing headlamp as the light source for an infrared light (for example, see Patent Document 2).
As shown in FIG. 9, the infrared light irradiating lamp for a vehicle comprises a halogen lamp 15 for emitting a light at least from a visible region to an infrared region, and a filter 17 for transmitting an infrared light in the lights emitted from the halogen lamp 15 and shielding a visible light. The halogen lamp 15 and the filter 17 are accommodated in one lamp unit and the filter 17 provided to be rotatable in an A direction around a pin 19 is rotated in the A direction so that the infrared light or a high beam is switched and emitted.    [Patent Document 1] JP-A-2004-87281 Publication    [Patent Document 2] JP-A-2004-71443 Publication